Antenna design ideas for radio amateurs by Rudy Severns N6LF

The design of antennas is a rich field for investigation and innovation. Even after more than a hundred years of work in the field we can still gain new insights and ideas. Since I was first licensed over 60 years ago antennas have been my passion and over the years I've published articles on antennas and continue to study and write about them.

Amateurs rarely design and build their own equipment these days but antennas are very often home brewed and provide a means for improving station performance at modest cost. 60 years ago Tom Erdmann, W7DND(SK), told me that if I had $100, I should spend the first $90 on the antenna, the next $9 for the receiver and the final $1 on the transmitter. Of course prices have gone up bit but those proportions are still sound advice. I can honestly say I have a lot more money invested in my antennas than in my station equipment.

This web site provides access to my articles and a place to post new work from time to time. Except for articles published elsewhere, much of what I'll be posting will be informal and subject to change as I learn more. The work reported here is a mix of analytic (calculations), NEC modeling and field experiments on actual antennas. Each of these has it's place but the best picture emerges when all three techniques are combined.

Please note, I try to close each post to comments. Once in a while I forget to push the right button and a post may be open. However, I assume I'm perfect and always have the posts closed, so I don't look for comments.

Some years ago I wrote a book on snubber circuits for power electronics. Strictly speaking this is not a hot topic for amateurs but I thought it might help a few so here it is: Download Snubber e-book complete . For those who don't need to know how to build the watch here's a much shorter summary: Download CD snubber design .

I have recently rebuilt my 630m antenna to use a counterpoise in place of the radial system of 128 wires lying on the ground. I wanted to see if a much simple counterpoise system would provide comparable efficiency. Take a look at: Download N6LF Transmit Antenna July 2017

For many months I've been working on a set of design notes LF-MF antennas intended for hams. I think the present draft, while far from perfect, may be helpful to many amateurs. For that reason I've posted the notes in their present form with the understanding they will be revised, probably several times, in the coming years.

By all means let me know if I've forgotten something useful and, even more importantly, if I've made a mistake! A lot of other peoples work is included but the mistakes are all mine!

Very often the wire available for an antenna will be wire intended for home electrical systems. This will is usually insulated which raises the question "should we strip off the insulation?" I took a very general look at this question using both experimental measurements and CAD modeling. Here are my observations: Download Insulated Wire and Antennas .

In addition to the base article there are several referenced articles which give additional information:

40 years ago Longmire and Smith suggested that the soil characteristics, conductivity and permittivity, which vary greatly with frequency, can be fitted to universal graphs. The idea is if you know the values at one frequency you can predict the values at a different frequency. I've had their report for many years but only recently took the time to carefully evaluate the idea. Attached is a scan of the original report, Download Longmire and Smith scan, an EXCEL spreadsheet containing their equations compared to independent measurements, Download Longmire and Smith graphs , and my comments on their idea, Download Comments on Longmire and Smith . The idea has some merit but you should decide for yourselves!

The March 2015 QST article on a loop receiving antenna by DK6ED set me to thinking about a much larger version for 2200m and up. In the process of scaling the antenna to my needs I realized that there several different operating modes (patterns) were possible which might be helpful in some situations. The different patterns could be implemented with some simple switching in the shack. I built that antenna and wrote an article published in Sept/Oct 2016 QEX: Download Sept-Oct 2016 QEX article .

The function in NEC which models wire insulation works only for thin layers of insulation, i.e. < one wire diameter and even that is pushing it a bit.

I tried to use this function to model buried radial systems with the wires in plastic tubes. All I got was nonsense! The EZNEC manual is very clear on this point but I couldn't resist trying it anyway!

For many years I have used soil probes and a network analyzer to measure my soil characteristics. It is also possible to determine soil properties using a low dipole. While this idea has been around for years it turns out to be a bit trickier than advertised. However, with a little care it can work just fine as I showed in my Nov/Dec 2016 QEX article: Download Soil characteristics QEX .